So you can show the actions and the concrete result. It's easier to show one time than to force your customers to read the manuals thousands of times.

If you are a teacher or representative of a company that develops software, then you simply have to make screencasts and show on a live example how to use your software or work according to your methodology.

A screencast is one of the best ways to explain to people how to use your product or how to effectively communicate with a program.